The examiner helps Harry out of the Great Hall and offers to let him return to finish, but Harry insists that he's done. As soon as he's alone, he races to the hospital wing and asks to speak to McGonagall. Madam Pomfrey explains that McGonagall is in St. Mungo's, and Harry feels alone and terrified. He sprints to find Ron and Hermione and pulls them into a classroom. Hermione's face turns white when Harry tells her that Voldemort has Sirius in the Department of Mysteries and plans to kill him. Harry sits down and asks how they're going to get there to rescue Sirius.
For Harry, who has distrusted his teachers throughout the year and refused to go for help, seeking out McGonagall suggests that at least in extremely dire situations, Harry does understand the importance of asking for help. This makes it even more tragic that, as far as Harry is concerned, there's nobody else here to help him, as he gets no positive reinforcement and again feels that he’s on his own.
Ron and Hermione look less convinced. Hermione wants to know how both Voldemort and Sirius, the two most wanted wizards in the country, got into the Ministry unnoticed. Ron, however, remembers Harry's dream of the snake biting Mr. Weasley and shifts to Harry's side. He suggests that since Regulus was a Death Eater, Sirius might know how to get the weapon. Hermione nervously points out that Harry likes to save people and Voldemort knows that Harry will want to save Sirius, so he could just be trying to lure Harry into a trap. Harry shouts that there's nobody else to ask for help, and refuses to believe that his dream was just a dream. He loses his temper with Hermione when she points out that both Dumbledore and Sirius wanted the dreams to stop.
Hermione makes a number of very valid points here, but because Harry is too caught up in his understandable and emotional desire to rescue Sirius, he's unable and unwilling to take any of her questions seriously. Once again, because Harry feels alone and doesn't have enough information to make truly informed choices, he's left jumping to conclusions and getting angry with Hermione for not supporting him fully.
Ginny and Luna walk in and ask if they can help. Harry rudely insists they can't, but Hermione says that they need to check if Sirius is home before they run to London. She suggests they use Umbridge's fire to contact him. Ron decides to tell Umbridge that Peeves is causing trouble, while Ginny and Luna decide to stand on either end of Umbridge's corridor to tell people someone let off Garroting Gas. Harry realizes this is a good plan, so he agrees and gets his Invisibility Cloak. Everyone takes their places and when the corridor is clear, Hermione and Harry sneak into the office. Harry sticks his head in the fire. When he's at Grimmauld Place, he shouts for Sirius. Kreacher is in the kitchen and delightedly says that Sirius is in the Department of Mysteries.
Especially when Luna agrees to help, despite not knowing that Sirius is innocent or being connected with the Order of the Phoenix at all, it shows Harry that the D.A. was successful in helping him connect with classmates from other Houses. Were Harry thinking critically, Kreacher's delight that Sirius is gone would be a red flag—in reality, Kreacher is tricking Harry and is thrilled to be doing so. However, because Harry believes that Kreacher isn't necessarily capable of such a thing, the possibility never occurs to him.
Suddenly Umbridge drags Harry's head back through the flames until he's back in her office. Malfoy, Crabbe, and Goyle enter, holding Ron, Ginny, Luna, and Neville. Umbridge insists that Harry was plotting something and then sends Malfoy to fetch Snape. Harry can't believe he forgot about Snape. Snape enters and tells Umbridge that he can't procure more Veritaserum. Harry meets Snape's eyes and wills him to understand. Umbridge shrieks that Snape is on probation, and as Snape starts to leave, Harry shouts, "he has Padfoot at the place where it's hidden." Snape stares coldly at Harry and tells Umbridge that Harry's outburst was nonsense.
Padfoot was Sirius’s nickname at school, which Snape would surely be aware of. For Harry, having Snape tell him he's crazy to his face is devastating, as it means that the one person he thought he could count on to take him seriously isn't going to help him. However, Snape must also stay in character and not reveal that he knows what Harry is talking about, so he has no real choice but to treat Harry like a fool in front of Umbridge.
Umbridge starts to talk to herself and say that she has no choice but to use the Cruciatus Curse on Harry. She admits to sending the dementors over the summer to attack him and get him expelled. As she starts the incantation, Hermione says that they'll have to tell Umbridge the truth. Harry realizes that Hermione isn't actually crying tears, as she sobs that Harry was using the fire to try to tell Dumbledore that "the weapon" is ready. She says he left the students to finish it and they don't know how to tell him. Hermione agrees to show Umbridge the weapon and convinces Umbridge to come alone.
As expected, Hermione is able to prey on what she knows Umbridge is after (proof that Dumbledore is mobilizing students against the Ministry) and, with very little tangible information, Umbridge falls for it. By pulling Dumbledore into her tale, Hermione makes it even more compelling for Umbridge, since she hates Dumbledore so much. Her choice to use the Cruciatus Curse more explicitly links Umbridge with the kind of evil Voldemort is usually associated with, and shows how power corrupts and often leads to violence. Note also how Umbridge latches onto the concept of a “weapon,” just as the children did earlier.